外侧膈区氨基丁酸能神经元介导的海马-腹侧被盖区神经通路在吗啡条件性位置偏爱再次获得中的作用

The interaction of several brain area contributed to relapse to drug use, but the mechanisms mediated this relapse are unknown. Our prior studies found that intra-CA3 injection of TTX significantly blocked the reinstatement of morphine-induced conditioned place preference (CPP), and inhibited the upregulation of GAD 67 in the lateral septum (LS) induced by the reinstatement of morphine CPP. These results suggested that the GABA upregulation in the lateral septum mediated by CA3 might be involved in the reinstatement of morphine CPP. We also found that the GABAergic neuron in the lateral septum can projected to the VTA. Furthermore, intra-LS injection of semicarbazide, a GAD inhibitor, significantly blocked the reinstatement of morphine CPP and the GAD 67and GAD 65 decreases induced by the reinstatement of morphine CPP in the VTA. All these prior experiments implied that the activation of CA3 induced the activation of GABAergic neuron and the GABA expression in the LS, the released GABA in the VTA inhibited the expression of GABA in the VTA contributed to the reinstatement of morphine CPP. The present project focuses on the GABA of the LS and explored the role of CA3-LS-VTA neuronal pathway in the reinstatement of morphine CPP, investigate the modulation mechanisms of GABA in the LS by CA3 in the reinstatement of morphine CPP. Finally, to examine the mechanisms that GABA in the LS mediates the decreases of GABA in the VTA in the reinstatement of morphine CPP. Our project will provide novel therapeutic target for morphine addiction.

复吸是多个脑区共同参与的结果，确切的神经通路和分子机制并不清楚。我们最近发现海马内微量注射河豚毒素阻断吗啡条件性位置偏爱（CPP）再次获得，抑制外侧膈区γ-氨基丁酸合成限速酶GAD 67表达，提示海马通过影响外侧膈区γ-氨基丁酸的合成参与吗啡CPP再次获得。预实验进一步发现：外侧膈区氨基丁酸能神经元有投射到腹侧被盖区的神经纤维，且外侧膈区内微量注射GAD拮抗剂显著抑制吗啡CPP的再次获得和腹侧被盖区 GAD 67和65表达的下调。以上提示海马通过激活外侧膈区氨基丁酸能神经元，促进γ-氨基丁酸在腹侧被盖区的释放，进而抑制腹侧被盖区γ-氨基丁酸的表达，从而介导吗啡CPP的再次获得。本项目拟以外侧膈区γ-氨基丁酸为切入点，明确海马-外侧膈区-腹侧被盖区神经通路在吗啡诱导CPP再次获得中的作用；阐明外侧膈区γ-氨基丁酸上调及腹侧被盖区γ-氨基丁酸下调的分子机制。本项目为理解复吸具有重要的理论意义。

当今社会制约吸毒患者治疗的一个重要原因是难以控制的高复吸率，在生理基础上复吸是多个脑区共同参与的结果，但其中确切的神经通路和分子机制并不清楚。我们的实验研究发现：戒断大鼠吗啡CPP再次获得后，海马CA3区Fos的表达激活，外侧膈区GABA的表达上调，而海马内微量注射河豚毒素阻断吗啡CPP再获得，抑制外侧膈区γ-氨基丁酸合成限速酶GAD 67表达及神经元mEPSC的频率和幅度。这提示海马通过影响外侧膈区γ-氨基丁酸的合成参与吗啡CPP再次获得。进一步实验发现：外侧膈区氨基丁酸能神经元有投射到腹侧被盖区的神经纤维，且外侧膈区内微量注射GAD拮抗剂显著抑制吗啡CPP的再次获得和腹侧被盖区 GAD 67和65表达的下调；外侧隔区微量注TTX.，同样阻断吗啡诱导的CPP再获得。本项目明确了海马-外侧膈区-腹侧被盖区神经通路在吗啡诱导CPP再次获得中的作用，具体为海马通过激活外侧膈区氨基丁酸能神经元，促进γ-氨基丁酸在腹侧被盖区的释放，进而抑制腹侧被盖区γ-氨基丁酸的表达，从而介导吗啡CPP的再次获得。本项目为理解复吸的发生及机制具有重要的理论意义。